Avoid sentence fragments.

When you begin a sentence with a capital letter, and conclude
with an end mark, but forget to insert a main clause, you have
written a sentence
fragment.
This is a fierce error in writing. Read these examples:

Because hungry whales stormed the beach.

Running all over his new white sneakers.

To buy ice cream for his needy friend.

There is no main clause in any of the above and
therefore you have sentence fragments.

Read the revisions below. By adding a main clause
we complete the thought: